DESCRIPTION (Applicant's abstract): Approximately one-third of Americans will seek psychotherapy during their lives (Vandenbros, Cumming, & DeLeon, 1992). Though psychotherapy is often effective (Seligman, 1995), we know very little about why it is effective. Contemporary psychotherapy researchers have begun to argue that our progress toward understanding psychotherapy has been, in part, retarded by our reliance on controlled-group designs (Goldfried & Wolfe, 1996; Seligman, 1995; Siberschatz & Persons, in press). Though these designs have been very useful for demonstrating that psychotherapy works better than The proposed research will employ quantitative, single case methodology to test a series of hypotheses about the central role that a patients emotional responses to conditions of danger and/or safety in the therapeutic environment. These detection of dangerous versus safe conditions is known to trigger specific, observable emotional responses (e.g., changes in physiological arousal, and facial expression) in most living organisms (Gilbert 1993, 1995). This proposal outlines a rationale and a method for testing the theory that these specific, observable responses serve not only as the ingredients that determine the flavor of the therapy relationship but also as the compass that determines the course of psychotherapy. Three treatments will be studied. Clients will meet Diagnostic and Statistical Manual (4th ed.) criteria for a unipolar depressive disorder. Therapists will be supervised UC Berkeley graduate students. Sixteen sessions will be offered in each treatment. All sessions will be videotaped and transcribed to remove identifying information. During all sessions, both therapist and client physiology (e.g., heart rate, sweat gland activity) will be continuously measured. Therapeutic interventions will be rated to client emotional response and subsequent changes in progress and in the overall relationship.